If you are downloading a big file (or even a small one) and the connection breaks or times out, use this command in order to RESUME the download where it failed, instead of having to start downloading from the beginning. This is a real win for downloading debian ISO images over a buggy DSL modem.
Take the partially downloaded file and cat it into the STDIN of curl, as shown. Then use the "-C -" option followed by the URL of the file you were originally downloading.
Show Sample Output

This is sample output - yours may be different.

% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 17.1M 100 17.1M 0 0 746k 0 0:00:23 0:00:23 --:--:-- 793k

There's probably a more efficient way to do this rather than the relatively long perl program, but perl is my hammer, so text processing looks like a nail.
This is of course a lot to type all at once. You can make it better by putting this somewhere:
clf () { (curl -d "q=$@" http://www.commandlinefu.com/search/autocomplete 2>/dev/null) | egrep 'autocomplete|votes|destination' | perl -pi -e 's/<a style="display:none" class="destination" href="//g;s/<[^>]*>//g;s/">$/\n\n/g;s/^ +|\([0-9]+ votes,//g;s/^\//http:\/\/commandlinefu.com\//g'; }
Then, to look up any command, you can do this:
clf diff
This is similar to http://www.colivre.coop.br/Aurium/CLFUSearch except that it's just one line, so more in the spirit of CLF, in my opinion.
Show Sample Output

Retrieve the current stock price from Yahoo Finance. The output is simply the latest price (which could be delayed). If you want to look up stock for a different company, replace csco with your symbol.
Show Sample Output

What's this?

commandlinefu.com is the place to record those command-line gems that you return to again and again.
That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and
voted up or down.

Stay in the loop…

Follow the Tweets.

Every new command is wrapped in a tweet and posted
to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning,
there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.